Y-shaped magnetic core



March 1 1 W. C. HURT, JR

Y-SHAPED MAGNETIC CORE 3 She t 1 Filed Nov. 6, 1958 ayurtcjn March 14, 1961 w. c. HURT, JR

Y-SHAPED MAGNETIC CORE 3 Sheets-Sheet 2 Filed Nov. 6, 1958 Y-SHAPED MAGNETIC CORE Filed Nov. 6, 1958 s Sheets-Sheet :5 I

United States PatentO Y-SHAPED MAGNETIC CORE William C. Hurt, Jr., Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Filed Nov. 6, 1958, Ser. No. 772,369

Claims. (Cl. 29-15557) This invention relates to curved cores having three generally G-shaped sections which are connected together at their corresponding ends into a Y-shaped yoke. By the term curved core is meant a core having strip laminations which are bent to eliminate cross grain effect during transfer of magnetic flux between yoke and leg portions of the core.

This type of curved core is well known in the art. One prior art method of constructing this type of core is to take a continuous strip of core material and measure and cut the strip into segments. After this the segments are stacked and shaped into a core form and then annealed to give them a permanent set and relieve their strains. In order to get a good mechanical and magnetic joint in the Y-shaped yoke specially configured cuts in the strip or inserts in the Y-shaped yoke are employed. The special cuts are undesirable since then reversal of individual strips is required. The special inserts are undesirable since they increase the number of pieces to be handled.

It is an object of this invention to provide an improved method of making curved Yshaped cores which will overcome the disadvantages of the above-mentioned prior art method.

In my invention there is no measuring, cutting and shaping of segments before anneal. Instead, in one form of the invention two continuous strips are first wound into two core loops and then annealed. Then the two loops are cut into half sections. One of the half sections of one loop is reversed with respect to its other half section. That is, reversal of individual segments is not required. Then these two reversed half sections are joined with one of the half sections of the other loop. The cutting procedure employed in cutting the two core loops gives half turn segments which can be readily joined at their corresponding ends into a Y-shaped yoke which has butt joints which are fully lapped. The fourth or remaining half section of the two core loops is not waste but is usable with another core loop cut and reversed as the first core loop.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a perspective view of a curved Y-shaped core constructed in accordance with my invention,

Fig. 2 is a top view of the Y-shaped joint of Fig. 1,

Fig. 3 is an elevation view of a wound and annealed core loop which is going to be used to form core parts 1' and 2 of Fig. 1,

. Fig. 6 is a diagrammatic illustration of the method of making the core part 3 of Fig. 1.

' Patented Mar. 14, I961 Referring now particularly to Fig. 1, illustrated therein is a curved magnetic core which has three generally C-shaped core parts 1 to 3 which are joined together at their corresponding ends into the form of a Y-shape. The core parts 1 to 3 are laminated and their laminations are curved at their corners 4 where their yokes 5 and legs 6 merge. This type of core is used for three phase electrical transformers. In the finished transformer each of the legs 6 will be surrounded by an electrical winding. However, the windings have been omitted so as to better show the core. The electrical windings can be preformed and the laminations of the core parts 1 to 3 laced therethrough or the electrical windings can be wound on the core after it is assembled.

The method of forming the core parts 1 and 2 will be described first in connection with Figs. 3 to 5. The method comprises spirally winding a continuous strip 7 of magnetic material into a generally rectangular-shaped core loop such as 8 in Fig. 3. Preferably grain oriented magnetic strip is used in making all parts of the core. The core loop 8 has a plurality of radially nested turns which are given a permanent set and whose strains are relieved by annealing. The strip 7 does not necessarily have to be wound directly into a rectangular form. It could be wound into a circular or other form and then shaped into the desired shape before anneal. However, since the C-shaped parts 1 to 3 of the final core are to be in the general form of half rectangles, winding the strip directly into a rectangular-shaped core loop 8 is preferred.

After the core loop is annealed it is marked olf so that it can be cut in accordance with the invention. The marking comprises a groove 9 milled into one side of the core, in this instance the back side of the core. The groove 9 is formed in both the top and bottom of the core. Other marking means such as a drilled hole, paint, etc. can be used but a milled groove is preferred since then the core can be cut with an apparatus similar to that disclosed in my copending patent application Serial Number 715,543, filed February 17, 1958, and assigned to the same assignee as the instant application.

In the preferred form of the invention the core of Fig. l is symmetrical. That isto say, the parts 1 to 3 have an equal number of laminations Whose Width is W, are disposed degrees from each other and have the same configuration. When viewing the core loop 8 in its wound condition the plan of cutting is to out each layer at opposite ends of the core loop so that the whole core loop is cut into segments having a length of about /2 turn of the core loop. This is done by making parallel 30 degree angle cuts 10 at each end of the core alternately from opposite sides and ends of the core loop centerline 11 when viewing Fig. 4. Also, and still viewing Fig. 4, the shaded acute angled corners 12 of the ends of the half turn segments which extend past the centerline 11, are cut off by making parallel 60 degree angle cuts 13 at each end of the core alternately from opposite sides and ends of the core loop centerline 11. The centerline 11 is an imaginary line, forming a plane which bisects the core loop 8. As is clearly shown in Fig. 4, the corners 12 are cut from the cut ends of the laminations which extend or lie beyond this bisecting plane.

The core loop 8 can be cut as indicated in Figs. 3 and 4 by unwinding the strip 7 and using the cutting sequence shown in Fig. 5. In Fig. 5 the half turn segments have been shortened somewhat so as to simulate an appreciable length of the strip. When the strip 7 is laid out flat and out, the cutting sequence is to first make two 30 angle cuts 10a and 10b behind, that is on one side, andfrom opposite ends of the lines 11' which would correspond to the centerline 11. The next pair of 30" angle cuts 100 and d are parallel to the first pair 10a and 1%, respectively, but are made ahead of, that is on the other side of, the lines 11'. This pattern of a pair of cuts 10:: and 18b behind lines 11' and then a pair of cuts 10c and 10d ahead of lines 11' is repeated until all of the strip 7 is cut. The lines 11' or their equivalent could be marked oif on the opposite edges of the strip with paint or the like to locate the cuts. However, milled grooves 9 are preferred if apparatus similar to that disclosed in my copending patent application is used to cut the strip. It will be noted that the cuts of each pair 10a, 10b and 10c, 10d are disposed with respect to each other at an angle of 60 degrees.

The shaded sharp corners 12 of the ends of the segments which extend past the lines 11' are cut off along lines 13a, 13b, 13c and 13a. These cuts also fall in the sequence of first a pair behind the lines 11 and then a pair ahead of the lines 11 with the cuts of each pair alternating from opposite ends of the lines 11 but at an angle of 60 degrees. The second pair 130 and 13d parallel the first pair 130! and 13b, respectively, and the cuts of each pair of disposed with respect to each other at an angle 60 degrees.

Referring now back to Fig. 4, the left-hand section corresponds to part 1 of Fig. 1. After the right-hand section of Fig. 4 is reversed end for end, it will correspond to part 2 of the Fig. 1. After the left-hand section and the reversed right-hand section of Fig. 4 are each shifted rearwardly 30 degrees, so that these sections are disposed with respect to each other by an angle of 120 degrees, they will line up with each other as indicated in Figs. 1 and 2 so that the laminations of the third core part 3 of Fig. 1 can be alternately butted and lapped with the laminations of parts 1 and 2.

The method of making the remaining core part 3 will now be described in connection with Fig. 6 which illustrates diagrammatically the cutting plan with respect to a strip which has been wound into a rectangular shaped core loop 21 and annealed. The layers of each end of the core are cut at right angles to their side edges on alternate sides of the centerline 22 of the core loop and at a distance of W/ /3 from the centerline where W is the width of the strip used in core parts 1 and 2 which in this instance is also true for 'core part 3. This plan of cutting may be carried out by unwinding the strip 20 and making first two cuts behind marks on the strip corresponding to centerline 22 and then two cuts ahead of the marks and so on. The means for assisting in locating the cuts in the unwound strip may comprise a groove milled into the side of the core loop 21 along the centerline 22 in which event the apparatus of my copending patent application can be readily used to cut the core. In Fig. 6 the cuts to be made are indicated by the X marks. Assuming that the core of Fig. 6 has been cut at the X marks, it will be apparent that two half core sections are formed in which at each end thereof alternate segments overhang the others by 2W/x/3. Therefore, either of the half sections of Fig. 6 is usable for the third core part 3 of Fig. 1. The remaining section of Fig. 6 is not waste but is usable with another core loop similar to the one of Fig. 3.

In Figs. 3 to 6 the centerlines 11, 11', and 22 correspond to a plane which would centrally and longitudinally traverse the core loops perpendicular to their side edges.

As heretofore noted, the core of Fig. 1 can be assembled and then the electrical windings wound on the core legs 6. Alternately, preformed electrical winding cylinders can be used in 'which event the segments can be laced one at a time through each of the winding cylinders, or a plurality of segments can be laced together through each of the cylinders. As the core loops 8 and 21 are being cut their segments can be radially nested until cutting is completed and lacing can commence. However, if both core loops are cut at the same time and both of their strips are cut f o h inside to the .4 outside, lacing need not be delayed until the whole of both core loops is cut.

It will be obvious to those skilled in the art that each layer of the core can comprise two or more identical laminations. That is to say, both core loops 8 and 21 can comprise two or more strips which are simultaneously wound and then cut. Alternately, a core having multiple laminations in each layer can be obtained by using only a single strip in the core loops 8 and 21 by modifying the sequence of cutting. For instance, if a core having two identical laminations per layer were desired, the single strip'of core loop 21 would first be out four times behind the centerline 22 and then four times before the centerline. The strip 7 of core loop 8 would be cut first four times behind the centerlines 11 in the sequence of 10a, 10b, 10a, 10b and then four times ahead of the centerlines 11 in the sequence of 10c, 10d, llllc, 10d. That is to say, the pairs of cuts 10a, 10b and 10c, 1011 would be repeated before they are alternated by the number of laminations desired in a core layer.

To put it another way, the turns of both core loops are out along their length an even number of times first ahead and then the same even number times behind the centerlincs. If two strips are simultaneously wound into the core loops then cutting the turns twice ahead and then twice behind the centerlines will give a core with two laminations per layer. If three strips are used then the even number of two cuts ahead and behind the centerlines will give a core with three laminations per layer. An even number of four cuts would give a core with six laminations per layer. If a single strip is used but two laminations per layer are desired then the even number of four cuts will be used. If three laminations are desired then the even number of six cuts will be used.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention, and therefore, it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim. as new and desire to secure by Letters Patent of the United States is:

l. A method of making a curved Y-shaped core, said method comprising cutting two strip wound annealed core loops into half sections, reversing one half section of one core loop relative to its other half section, and assembling said relatively reversed half sections with a half section of the other core loop into said Y-shaped core, in said one core loop cutting the successive layers at each end thereof with the cut extending from alternate ends of a plane bisecting said loop'and having such alternate ends on opposite sides or" said loop in parallel directions at an angle of 30 degrees from said plane, cutting off the acute angled corners of the cut ends of said layers which lie beyond said plane with the cuts extending from the ends of said plane at an angle of 60 degrees from said plane, and in said other core loop cutting the successive layers at each end thereof parallel to and equidistantly from alternate sides of its bisecting plane.

2. A methodof making a curved Y-shaped core, said method comprising winding magnetic core strip material into two generally rectangular-shaped core loops having a plurality of radially nested turns, annealing said core loops, cutting said core loops into half sections, reversing one half section of one core loop relative to its other half section, and assembling said relatively reversed half sections with a half section of the other core loop into said Y-shaped core, in said one core loop cutting the successive turns at each end thereof in parallel directions'at an angle of 30 degrees from a plane bisecting said loop and having ends on opposite sides of said loop alternately from opposite ends of said plane, cutting off the acute angled corners of the cut ends of said turns which lie beyond said centerline at an angle of 60 degrees from said plane with the cuts extending from the ends of said plane, and in said other core loop cutting the successive turns at each end thereof parallel to and equidistantly from alternate sides of its bisecting plane.

3. A method of making a curved Y-shaped core, said method comprising cutting two strip wound annealed core loops into half turn segments, successively cutting the turns of one core loop along their length first two times on one side and then two times on the other side of imaginary lines on said turns corresponding to the centerline of said one core loop, said imaginary lines extending across said strip wound core loop having its ends on opposite sides of the strip forming said loop and forming a plane which bisects said one core loop, all of the cuts being made from the ends of said lines at an angle of 30 degrees from said lines with immediately successive cuts being disposed with respect to each other at an angle of 60 degrees when said turns are in a straight condition, and cutting off the acute angled corners of the cut ends of turns which extend on either side of said lines from the ends of said lines at an angle of 60 degrees from said lines, successively cutting the turns of the other core loop along their length first two times on one side and then two times on the other side of its successive imaginary lines parallel to and equidistantly from its imaginary lines, reversing the half turns from one side of said one core loop with respect to its other half turns, and alternately butting and lapping the ends of said relatively reversed half turns with the ends of the half turns from one side of said other core loop into said Y-shaped core.

4. A method of making a curved Y-shaped core, said method comprising winding magnetic core strip material into two generally rectangular shaped core loops having a plurality of radially nested turns, annealing said core loops, successively cutting along their length the turns of one core loop first two times on one side and then two times on the other side of imaginary lines on said turns corresponding to the centerline of said one core loop, said imaginary lines extending across said strip material forming said core loop having its ends on opposite sides of the strip material forming said loop and forming a plane which bisects said one core loop, all of the cuts being made from the ends of said lines at an angle of 30 degrees from said lines with immediately successive cuts being disposed with respect to each other at an angle of degrees when said turns are in a straight condition, and cutting off the acute angled corners of the cut ends of turns which extend on either side of said lines from the ends of said lines at an angle of 60 degrees from said lines, successively cutting along their length the turns of the other core loop first two times on one side and then two times on the other side of its successive imaginary lines parallel to and equidistantly from its imaginary lines, reversing the half turns from one side of said one core loop With respect to its other half turns, and alternately butting and lapping the ends of said relatively reversed half turns with the end of the half turns from one side of said other core loop into said Y-shaped core.

5. A method of making a curved Y-shaped core, said method comprising cutting the turns of two wound annealed core loops into half turns, successively cutting the turns of one core loop along their length first an even number of times on one side and then the same number of times on the other side of imaginary lines on said turns corresponding to a central and perpendicular plane through said one core loop, said imaginary lines extending across said turns and having ends on each side of said turns, all of the cuts being made from the ends of said lines at an angle of 30 degrees from said lines with immediately successive cuts being disposed with respect to each other at an angle of 60 degrees when said turns are in a straight condition, and cutting off the acute angled corners of the cut ends of turns which extend on either side of said lines from the ends of said lines at an angle of 60 degrees from said lines, successively cutting the turns of the other core loop along their length the same even number of times as in said one core loop first on one side and then on the other side of its successive imaginary lines parallel to and equidistantly from its imaginary lines, reversing the half turns from one side of said one core loop with respect to its other half turns, and alternately butting and lapping the ends of said relatively reversed half turns with the ends of the half turns from one side of said other core loop into said V-shaped core.

References Cited in the file of this patent UNITED STATES PATENTS 2,305,650 Vienneau Dec. 22, 1942 2,367,927 Chllbb Jan. 23, 1945 2,594,002 Ellis et a1. Apr. 22, 1952 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No.., 2,974,402 March 14, 1961 William C Hurt Jr It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 2, for lcenterline" read plane Signed and sealed this 15th day of August 1961-,

(SEAL) Attest:

' ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No as, 2,974 402 March 14 v 1961 William (3., Hurt Jr It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line .2 for .".,centerline:" read plane Signed and sealed this 15th day of August 1961' (SEAL) Attest:

' ERNEST W. SWIDER DAVID L. LADD Attesting Officer I Commissioner of Patents 

